jQuery.base64 = (function ($) {

    var _PADCHAR = "=",
        _ALPHA = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/",
        _VERSION = "1.1";//Mr. Ruan fix to 1.1 to support asian char(utf8)


    function _getbyte64(s, i) {
        // This is oddly fast, except on Chrome/V8.
        // Minimal or no improvement in performance by using a
        // object with properties mapping chars to value (eg. 'A': 0)

        var idx = _ALPHA.indexOf(s.charAt(i));

        if (idx === -1) {
            throw "Cannot decode base64";
        }

        return idx;
    }

    function _decode_chars(y, x) {
        while (y.length > 0) {
            var ch = y[0];
            if (ch < 0x80) {
                y.shift();
                x.push(String.fromCharCode(ch));
            } else if ((ch & 0x80) == 0xc0) {
                if (y.length < 2) break;
                ch = y.shift();
                var ch1 = y.shift();
                x.push(String.fromCharCode(((ch & 0x1f) << 6) + (ch1 & 0x3f)));
            } else {
                if (y.length < 3) break;
                ch = y.shift();
                var ch1 = y.shift();
                var ch2 = y.shift();
                x.push(String.fromCharCode(((ch & 0x0f) << 12) + ((ch1 & 0x3f) << 6) + (ch2 & 0x3f)));
            }
        }
    }

    function _decode(s) {
        var pads = 0,
            i,
            b10,
            imax = s.length,
            x = [],
            y = [];

        s = String(s);

        if (imax === 0) {
            return s;
        }

        if (imax % 4 !== 0) {
            throw "Cannot decode base64";
        }

        if (s.charAt(imax - 1) === _PADCHAR) {
            pads = 1;

            if (s.charAt(imax - 2) === _PADCHAR) {
                pads = 2;
            }

            // either way, we want to ignore this last block
            imax -= 4;
        }

        for (i = 0; i < imax; i += 4) {
            var ch1 = _getbyte64(s, i);
            var ch2 = _getbyte64(s, i + 1);
            var ch3 = _getbyte64(s, i + 2);
            var ch4 = _getbyte64(s, i + 3);

            b10 = (_getbyte64(s, i) << 18) | (_getbyte64(s, i + 1) << 12) | (_getbyte64(s, i + 2) << 6) | _getbyte64(s, i + 3);
            y.push(b10 >> 16);
            y.push((b10 >> 8) & 0xff);
            y.push(b10 & 0xff);
            _decode_chars(y, x);
        }
        switch (pads) {
            case 1:
                b10 = (_getbyte64(s, i) << 18) | (_getbyte64(s, i + 1) << 12) | (_getbyte64(s, i + 2) << 6);
                y.push(b10 >> 16);
                y.push((b10 >> 8) & 0xff);
                break;

            case 2:
                b10 = (_getbyte64(s, i) << 18) | (_getbyte64(s, i + 1) << 12);
                y.push(b10 >> 16);
                break;
        }
        _decode_chars(y, x);
        if (y.length > 0) throw "Cannot decode base64";
        return x.join("");
    }


    function _get_chars(ch, y) {
        if (ch < 0x80) y.push(ch);
        else if (ch < 0x800) {
            y.push(0xc0 + ((ch >> 6) & 0x1f));
            y.push(0x80 + (ch & 0x3f));
        } else {
            y.push(0xe0 + ((ch >> 12) & 0xf));
            y.push(0x80 + ((ch >> 6) & 0x3f));
            y.push(0x80 + (ch & 0x3f));
        }
    }


    function _encode(s) {
        if (arguments.length !== 1) {
            throw "SyntaxError: exactly one argument required";
        }

        s = String(s);
        if (s.length === 0) {
            return s;
        }

        //s = _encode_utf8(s);
        var i,
            b10,
            y = [],
            x = [],
            len = s.length;
        i = 0;
        while (i < len) {
            _get_chars(s.charCodeAt(i), y);
            while (y.length >= 3) {
                var ch1 = y.shift();
                var ch2 = y.shift();
                var ch3 = y.shift();
                b10 = (ch1 << 16) | (ch2 << 8) | ch3;
                x.push(_ALPHA.charAt(b10 >> 18));
                x.push(_ALPHA.charAt((b10 >> 12) & 0x3F));
                x.push(_ALPHA.charAt((b10 >> 6) & 0x3f));
                x.push(_ALPHA.charAt(b10 & 0x3f));
            }
            i++;
        }


        switch (y.length) {
            case 1:
                var ch = y.shift();
                b10 = ch << 16;
                x.push(_ALPHA.charAt(b10 >> 18) + _ALPHA.charAt((b10 >> 12) & 0x3F) + _PADCHAR + _PADCHAR);
                break;

            case 2:
                var ch1 = y.shift();
                var ch2 = y.shift();
                b10 = (ch1 << 16) | (ch2 << 8);
                x.push(_ALPHA.charAt(b10 >> 18) + _ALPHA.charAt((b10 >> 12) & 0x3F) + _ALPHA.charAt((b10 >> 6) & 0x3f) + _PADCHAR);
                break;
        }

        return x.join("");
    }


    return {
        decode: _decode,
        encode: _encode,
        VERSION: _VERSION
    };

}(jQuery));
